Facilitated diffusion has been considered in the literature mainly as a process occurring in a homogeneous medium. The exception to this has been consideration via paths in parallel. A broader look at this problem has been initiated by those interested in the transport in the blood and the cellular uptake of fatty acids, which are bound to albumin in the blood and by fatty acid binding protein in many cells. In this project we will undertake a series of studies of gradually increasing complexity concerning such diffusional facilitation, specifically examining the combined kinetics of rates of adsorption and desorption of substrates to carrier proteins and the relationship between these and the rates of transmembrane transport by various mechanisms. An overview of the processes involved in fatty acid transport is provided by Bassingthwaighte et al. (1989) for the heart. Fleischer (1986) and, for example, Burczynki et al. (1989) explored hepatocyte uptake. To undertake a carefully staged sequence of studies on the transport of solutes within homogeneous regions in series with transport across barrier membranes. The transmembrane transport processes will include different types of mediated transport, and complex interactions between the facilitating binding molecules in the homogenous regions with the specialized transporters will be considered.